Such a current limiter is intended to be used in series with a circuit breaker and serves to greatly reduce the amplitude of fault current by limiting the value of the current it conveys, thereby reducing electrodynamic forces on circuit breaker apparatus and also reducing the energy of the arc to be interrupted therein.
Such a limiter conventionally comprises an element made of a material suitable for taking up the superconducting state, for example but not exclusively niobium-titanium placed in liquid helium.
In the event of current intensity increasing (e.g. due to a short circuit), the current exceeds the critical value and the element returns to a state having a high value of resistance, thereby limiting the current. The superconducting element is generally made in the form of a coiled wire of sufficient size and length to be able to withstand the reestablished voltage for a certain length of time until the series-connected circuit breaker opens.
One difficulty lies in making a coil whose self-inductance is small enough to avoid reactive losses in normal operation. The prior art coil is conventionally constituted by two or four coils connected in series which are wound coaxially in opposite directions relative to one another. This solution is not easily adapted to high tension grids because of the problem of providing insulation between the inlet and the outlet of the coil.
The problem of insulating the inlet and the outlet can be solved by using parallel concentric coils wound in opposite directions, however when using superconducting wires, this solution can give rise to high loop currents because of the substantially zero electrical resistance.
Even when two coils are perfectly wound for minimizing self-inductance, any small internal or external disturbance can give rise to an untimely transition of the superconductor.
The invention proposes a solution which is simple, convenient to implement, and reliable.